Avoiding Wake Turbulance in the air

[SixPapaCharlie]

In my training, they drilled in the when to land and takeoff behind a large plane. I am not sure I was given a lot of instruction on avoiding it in the air.

Yesterday I am at 1500 under the 2k level of the bravo.
ATC says "Heavy 2 miles, 12 O'Clock, Caution wake turbulence"

He crosses my path at a right angle about a minute to a minute and a half in front of me. I would estimate he is about 500 feet above me.

I am throwing out 747, could have been an airbus. 4 engines though.

I realize I have no idea how fast the wake sinks and really have no idea what to do.

I dropped down to 1000 feet and just crossed my fingers that he didn't spin me into shrapnel.

What is a good policy for avoiding this? I know they spin out and down but I have no idea how fast and I have no rule of thumb for ensuring I am clear of it. I think in pictures so below is sort of the scenario.

I lived and didn't feel anything but I was on edge and didn't know what was enough to confirm I was clear.

 

[COFlyBoy]

I don't have a rule of thumb for you, but I have flown through the wake of an RJ. Our flight path was perpendicular, and we were about 1000' below. It was just a big bump, and that was it.
Might be a much bigger bump for a heavy, but I'm not sure you'd need to avoid it if you are heading perpendicular. You'll only be in the wake for a 1/2 second, maybe 1 second if you are going slow.

 

[Archammer]

Yes, I agree. Thinking about the wind motion, going across it, would be similar to a boat over the wake of another going across you. You would have a brief moment of up and down (y axis) motion and then again through the other side. No loss of control issues there.

In my opinion, the issue with the wake would be following it as the motion of the air would create the lift on one side and down force on the other, causing the rolling action. That in conjunction with the pitch up and down is where that roll / spin action is so dangerous.

Glad you're ok though, and this is good information to have, as I haven't really thought of it much until you mentioned your story.

Good stuff!

 

[Shawn]

but I'm not sure you'd need to avoid it if you are heading perpendicular. You'll only be in the wake for a 1/2 second, maybe 1 second if you are going slow.

...you sure as heck do! I was at 3000' and crossed perpendicular a 747 heavy's path climbing out of SFO. He was a a good several miles outbound of my path and I THOUGHT I was a good 500' above his departure path at my crossing point...WRONG! We got tossed HARD and all hit the ceiling, everything in the plane was tossed upside down.

I have had just minor bumps in the past in similar situations so didn't think much of it ahead of time.

That was the day I TRULY learned what ATC's "caution, wake turbulence" meant!

Here is great link to an FAA AC on wake turbulence that is actually really well done and may answer some of your questions:

http://rgl.faa.gov/Regulatory_and_G...40310a35286257c7c00720481/$FILE/AC 90-23G.pdf

 

[SixPapaCharlie]

I thought I saw somewhere on here where a small plane flew perpendicular through heavy wake and it rolled the plane end over end??

 

[SixPapaCharlie]

Here it is:
http://www.pilotsofamerica.com/forum/showpost.php?p=1242014&postcount=79

 

[Shawn]

A roll from wake turbulence should be fully recoverable except for that whole lack of altitude thing.

 

[EdFred]

Just heed the words of Steve Winwood.

 

[bobmrg]

In my training, they drilled in the when to land and takeoff behind a large plane. I am not sure I was given a lot of instruction on avoiding it in the air.

Yesterday I am at 1500 under the 2k level of the bravo.
ATC says "Heavy 2 miles, 12 O'Clock, Caution wake turbulence"

He crosses my path at a right angle about a minute to a minute and a half in front of me. I would estimate he is about 500 feet above me.

I am throwing out 747, could have been an airbus. 4 engines though.

I realize I have no idea how fast the wake sinks and really have no idea what to do.

I dropped down to 1000 feet and just crossed my fingers that he didn't spin me into shrapnel.

What is a good policy for avoiding this? I know they spin out and down but I have no idea how fast and I have no rule of thumb for ensuring I am clear of it. I think in pictures so below is sort of the scenario.

I lived and didn't feel anything but I was on edge and didn't know what was enough to confirm I was clear.

I crossed beneath the wake of a pair of military jets just east of Luke AFB...they were out of sight by the time I hit the turbulence, but I hit my head on the headliner anyway.

Best info I have is that the turbulence descends about 900 feet and stays there, so I would want to be at least 1000' beneath the flight path of the biggie.

Bob Gardner